Messages in this thread | | | Date | Tue, 26 Jul 2022 14:46:57 +0800 | Subject | Re: [PATCH v2] USB: HCD: Fix URB giveback issue in tasklet function | From | "" <> |
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On 2022/7/25 21:58, Alan Stern wrote: > On Mon, Jul 25, 2022 at 02:52:51PM +0800, Weitao Wang wrote: > > This is basically okay. Just a couple of small comments... > >> Usb core introduce the mechanism of giveback of URB in tasklet context to >> reduce hardware interrupt handling time. On some test situation(such as >> FIO with 4KB block size), when tasklet callback function called to >> giveback URB, interrupt handler add URB node to the bh->head list also. >> If check bh->head list again after finish all URB giveback of local_list, >> then it may introduce a "dynamic balance" between giveback URB and add URB >> to bh->head list. This tasklet callback function may not exit for a long >> time, which will cause other tasklet function calls to be delayed. Some >> real-time applications(such as KB and Mouse) will see noticeable lag. >> >> Fix this issue by taking new URBs giveback in next tasklet function call. >> Add a member high_prio for structure giveback_urb_bh and replace the local >> high_prio_bh variable with this structure member in usb_hcd_giveback_urb. > > The patch description should do more than say what the new code _is_ -- > we can see that easily enough by reading the patch. The description > should explain _why_ the code was changed. > Okay, I will improve this patch description.
>> - /* check if there are new URBs to giveback */ >> + /* giveback new URBs next time to prevent this function from >> + * not exiting for a long time. >> + */ > > Minor stylistic issue: The currently accepted format for multi-line > comments is like this: > This notes will be improved in next patch version also. Thanks for your suggestion.
weitao > /* > * Blah blah blah > * Blah blah blah > */ > > Alan Stern > .
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